The invention generally relates to magnetorheological (MR) fluid devices, and more specifically the invention relates to a magnetorheological fluid based joint for selectively and releasable joining at least two discrete members in fixed abutment.
Generally, magnetorheological fluid devices include a volume of MR fluid, comprised of a fluid medium having magnetizable particles suspended in a viscous liquid carrier such as oil. When a magnet is applied to the MR fluid, the particles are magnetized and as a result are held in place by the applied magnetic field. The magnetizable fluid assumes a near-solid state when the magnetic field is applied. When the magnet is removed from its position proximate the MR fluid, the MR fluid returns to its viscous liquid state.
MR fluid devices are typically comprised of rotary and linear acting dampers. The rotary devices are frequently used as brakes, clutches and the like for providing variable torques while linear acting devices are frequently used for damping linear motion or for providing controllable dissipative forces along a specified axis. In such typical applications of the MR fluid based technology, a magnetic field is applied across the MR fluid in order for the device to provide the requisite resistance to motion or displacement and thereby supply the requisite braking or damping. The required magnetic field is determined by one or more operating variables of the device such as the speed of a device component. Thus the magnetic field required to produce the desired braking or damping is applied across the medium for the required period of time and at the required intensity.
By using MR fluid in such mechanical devices, a significant portion of the devices"" mechanical componentry having an associated finite life may be replaced by the MR devices having a useful life that is typically significantly greater than the replaced mechanical components.
In addition to the foregoing, it would be beneficial to use the field responsive material joint for connecting discrete members. By incorporating a volume of field responsive material in a joint, mechanical fasteners and other components may be eliminated and discrete members may be connected and disconnected easily and reliably.
The foregoing illustrates limitations known to exist in present MR devices and methods. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully described hereinafter.
In one aspect of the invention this is accomplished by providing a temporary joint comprising a first discrete member having a first movable coupling member and a second discrete member having a second movable coupling member. The first coupling member comprises a closed housing defining a chamber, a volume of a field responsive material such as magnetorheological (MR) fluid in a portion of the chamber, a material transfer member in the chamber and means for moving the transfer member to thereby move the material to the desired location in the chamber. The second coupling member comprises a field generating member such as a magnet. When it is necessary to couple the discrete members, the field responsive material is moved to the position in the chamber proximate the field generating means. As the field generating means is located proximate the material the discrete members are coupled. In order to uncouple the members, the transfer member is actuated to move the field responsive material away from the field generating member. Alternatively, the field generating member may first be removed from its location proximate the field responsive material.
The second coupling member may be comprised of a arcuate magnet, a solid pole piece, a slotted pole piece or a magnet supported by a holder.
In the first coupling member the transfer member may comprise a wedge shape or a bow tie shape and may be moved by a lever, a knob or by the second coupling member. By the joint of the present invention, the discrete members may be coupled in the same plane or may be separated by an angle.
The foregoing and other aspects of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.